The process of designing a mechanical part has been changed significantly by the widespread use and tremendous capability of computer aided drafting and computer aided design (CAD) tools. As the speed of computing power has increased and the attendant cost has decreased, the volume and type of design work performed with the assistance of a computer has expanded dramatically. In almost every industry the computer has become the design engineer""s tool of choice for crafting everything from the most simple of designs to completely integrated systems. Current technology provides for the computerized integration of the entire product lifecycle, including design, simulation, manufacturing, service and retirement. Descriptions of state-of-the-art computer aided design tools can be found by visiting the Internet home page of the assignee of the present invention at www.ptc.com.
The simplicity of generating, saving and retrieving digital models of parts has resulted in an explosion in the number of part designs that are stored in the computers of engineering firms, industrial corporations and CAD product and service providers. For example, the InpartSM database of the assignee of the present invention includes over a million three-dimensional part models as of the filing date of this invention. Such inventories of existing designs can prove very useful to a designer who has the ability to extract an existing design for use on a new project. Unfortunately, the industry""s ability to extract a useful design has not kept pace with its ability to create and to save such designs. In some cases, the designer may know of an existing part model or its identification code and is able to open the associated data file on a CAD tool. The InpartSM service offered by the assignee of this invention allows a user to browse through a directory structure to identify a category of parts similar to that desired by the user. For example, a user wishing to find a design for a waterproof 9-pin electrical connector can follow a series of branching decisions leading from electrical parts generally, to electrical connectors, to waterproof connectors, to 9-pin connectors. The system will then present a listing of part designs contained in that branch of the directory. While this type of searching tool has proven very useful, it is limited by the level of detail into which the various part models are categorized in the predefined directory structure.
Existing CAD systems have the capability of very accurately comparing two known part models, or of comparing a part model with inspection data from a manufactured part. U.S. Pat. No. 5,442,572 dated Aug. 15, 1995, and U.S. Pat. No. 5,848,115 dated Dec. 8, 1998, both incorporated by reference-herein, describe known methods for the comparison of an actual part geometry to a predetermined geometry. These methods involve the comparison of parts on a point by point basis. Furthermore, the Pro/VERIFY(trademark) program sold by the present assignee utilizes a technique for matching clouds of points in order to compare automated inspection data to a solid part model. This capability is very helpful in a manufacturing or quality control application, however, it is of limited usefulness to a user searching for a particular part design, since the specific model to be used in the comparison must be identified by the user, and the associated data file must be opened by the CAD tool.
When designing new products, the manufacturing industry often re-uses existing designs or portions of existing designs. As new computerized part models are created, there is a potential for the same part or a similar part to be duplicated across several products and product lines. This duplication generates cost as a result of the duplication of part numbers and drawings, the loss of volume discounts resulting from the unknowing use of multiple vendors, and the maintenance of duplicated inventory volumes. The more new parts that are created, the greater the potential for the unnecessary duplication of part designs.
Thus there is a particular need for a rapid method of comparing parts. Such a method should permit a user to rapidly search for a matching or similar part design stored in any collection of model data containing a large number of existing part designs.
Accordingly, a method of comparing parts is disclosed herein, the method comprising the steps of: compiling a database representing a plurality of parts, each part represented uniquely in the database by metadata representing the geometry of the part; determining corresponding metadata representing the geometry of a subject part; and identifying a range of values associated with the metadata of the subject part; and searching the database to identify all ones of the plurality of parts having metadata within the range of values. The metadata utilized in this method may include values representing the volume, surface area, and the principal moments of inertia of a part. The metadata may also include values representing the location of the cross-sectional center of gravity with respect to the point of intersection of the principal moments, for each of the planes of the principal moments.
A further method of comparing parts is disclosed herein, the method comprising the steps of: compiling a database representing a plurality of parts, each part represented in the database by values representing the volume, surface area, and principal moments of inertia of the part; determining values representing the volume, surface area and principal moments of inertia of a subject part; identifying a range of values associated with each of the volume, surface area, and principal moments of inertia of the subject part; and searching the database to identify all ones of the plurality of parts having values representing volume, surface area, and principal moments of inertia within each of the respective ranges of values.